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L. L. RUGGLES AUTOMATIC TELEPHONE SYSTEM May 9, 1933.

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Original Filed March 26, 1925 Inuan or Lennard L Ru Reissuecl May 9,1933 UNITED STATES PATENT OFFICE LEONARD L. RUGGLES, or WHEATQN,ILLINOIS, Assrenon, BY lvxnsivn ASSIGNMENTS,

TO ASSOCIATED ELECTRIC LABORATORIES, INC., OF CHICAGO, ILLINOIS,

RATION OF DELAWARE A CORPO AUTOMATIC TELEPHONE SYSTEM Original No.1,721,640, dated July 23, 1929, Serial No. 18,368, filed March 26,1925.- Renewed October 22,

The present invention relates to automatic telephone systems in general,but is concerned more particularly with automatic telephone systems inwhich directors are employed to translate the oflice digits of thetelephone numbers into the codes necessary to efiect the trunking of thevarious calls to the desired oilices by way of the most suitable paths;and the principal feature of the invention consists in the provision ofnew and improved circuit arrangements whereby the path over which adirector routes a particular call is made dependent upon the busy oridle condition of the trunk groups which may be encountered.

The invention is illustrated herein in connection with a systemcomprising a multioiiice network in which the offices comprising themain network are more or less closely grouped, geographically, and inwhich there is one small ofiice located at some distance from the mainnetwork but connected to the network through the medium of trunk linesrun between the outlying office and the near est mice in the network.

It is assumed that the majority of calls originated in the outlyingoffice are local calls. This situation may arise in case the ofiiceserves a manufacturing town or other settlement which has only slightbusiness and social connections with the district served by the mainpart of the network.

By way of example, it is assumed that not more than 2000 lines are usedat present in the outlying office and that these lines are reached byway of the fourth and fifth levels of the thousands selectors.Accordingly, in the ordinary procedure, the remaining levels of thethousands selectors would be left dead for the time being. In this case,however, it is proposed to use the thousands selectors for handling allcalls, in which case a thousands selector is also an ofiice selector, soto speak, in that it sends a call to one of the two local thousand linegroups or to the group of outgoing trunk lines, depending upon the digittransmitted to it.

It has been assumed that, due to the local conditions set forth above,thirty trunk lines combined into one group Will handle the Serial No.549,780.

traffic originated in the outlying ofiice and intended for the otheroflices in the network. The ordinary way of securing a thirty-trunkgroup of trunk lines is to use outgoing secondary line switches and toprovide (in the case of plunger type secondary line switches) threeseparate groups of secondary line switches, each group having access toa: separate trunk group of ten trunks each, and to split the outgoingselector bank multiple into as many groups as may be necessary in orderto secure a sutlicient number of primary trunks to handle the traiiicdirected to the secondary group. The above arrangement is well known, ofcourse, and it is merely pointed out herein order to contrast it withthe arrangement contemplated in the present case.

According to the present invention, three levels (instead of one) of thethousands selectors are taken over for use in connection with the abovementioned group of thirty direct trunks, namely, the third, sixth, andninth levels, ten trunks being taken from each of the three levels. Now,since directors are used to route the calls, any one dircctor may becross-connected so as'to send all outgoing calls which it handles by wavof any one of the three outgoing levels. Ac cordingly, the directors aresplit intothree groups from this standpoint. The directors of one groupare cross connected so that they send calls out over the ninth level;the directors of another group are cross connected so that they sendcalls out over the sixth level; and the directors of the other group arecross connected so that they send calls out over the third level.

The above is the normal arrangement, but when one level becomes busy,for example, the ninth level, the cross connecting in the directorswhich normally send trafiic out over the ninth selector level is changedby means of a relay arrangement so that the calls are sent out over thesixth level, provided it not also busy, and are sent out over the thirdlevel instead if the sixth level is busy.

In the case of the directors which normally send calls out over thesixth selector level, they are arranged to send their traffic out overthe third level in case the sixth level becomes busy, and to send thecalls to the ninth level in case the third level is busy also.

Similarly, the directors which normally send calls to the third levelare arranged so as to send the calls to the ninth level when the thirdlevel becomes busy, provided the ninth level is not also busy, and tosend the calls instead to the sixth level if the ninth level is busy.

The arrangement for accomplishing the above results consists in theprovision of chain relays. These relays pull up when all the trunks inthe respective groups become busy, and the arrangement is such that theycontrol the operation of the various groups of directors to bring aboutthe results above set forth.

Referring now to the drawings, they show by means of the usual circuitdiagrams a sufficient amount of the apparatus in a telephone systemembodying the principles of the invention to enable the invention to beunderstood and its utility to be appreciated.

Fig. 1 shows the first selector FS which is accessible to line switchesat terminals such as 2, 3, and 4, and which has access to local hundredsselectors and to the three subgroups of outgoing trunk lines. Thisdrawing shows also the trunk circuit TC which is inserted in the trunkline leading to the first selector FS and which has associated therewiththe director selector DS.

It will be noted that the circuits of the first selector F S are notshown in full and it is tobe understood that any one of severalwell-known two-wire selector circuits may be used.

Fig. 2 shows the repeaters R, R and R inserted in three outgoing trunklines, one trunk line in each of the three out-going subgroups, togetherwith the chain relay group CRG comprising the chain relays 109, 110, and111, which are used to control certain trunking operations of thedirectors.

Figs. 3-6 show one of the directors accessible to the director selectorDS, Fig. 1.

Referring now to Figs. 36, the portion of the director shown in Fig. 3includes the sequence switch S, which is used primarily to connect theincoming impulse conductor to the various operating magnets of thedirector in the proper order, and it accordingly moves one step at thetermination of each series of impulses. This switch is used also tostart the operation of the sender, Fig.

interrupter 320, together with relays 3 02 and 303 and the sendingswitch SS. This drawing shows also tie release relay 301, whichenergizes when the director is seized and which falls back when thedirector is freed.

Fig. 5 shows the oflice register OR which responds to the two officedigits of any number to bring the wipers 4124:15 into engagement withthe set of bank contacts corresponding to the called oilice.

Fig. 6 shows the digit registers DR1 DR-4L which respond to the foursubscriber digits, respectively, of a number and set their wipers uponthe respective impulse stop conductors corresponding to such digits.

The apparatus having been described generally, a detailed description ofthe operation will now be given. For this purpose it will be assumedthat a subscriber, desiring to call a subscriber whose line terminatesin the distant office reached by way of the third, sixth, and ninthlevels of the first selector FS, removes his receiver.

When this subscriber removes his receiver, his individual line switchoperates in the usual manner to select an idle trunk. In this case itwill be assumed that the trunk comprising conductors 57 and leading tothe trunk circuit TC is seized by the calling line switch at theterminals 2-a. When this occurs, line relay 8 of the trunk circuit TCenergizes over conductors 5 and 7 and over the calling line. At armature11, relay 8 closes a circuit for the slow acting release relay 9, whichthereupon energizes and places ground upon release trunk conductor 6 atarmature 13, thereby establishing the usual holding circuit to maintainthe seizing line switch operated after its slow acting line relay hasfallen back.

As a further result of the above mentioned operation of the slow actingrelease relay 9, it connects the test wiper 50 of the director selectorDS to the junction of switching relay 4 and stepping magnet 42 atarmature 15, and at armature 14 closes a circuit through switching relay4; and stepping magnet 42 in series. From this point, the operationdepends upon whether the director upon which the wipers of the directorselector DS are standing is busy or idle. If it is idle, the operationof armature 15 of relay 9 does not produce any particular effect at thistime and switching relay 4 energizes, seizing the director.

Assuming, on the other hand, that the director in question is busy, theground potential encountered upon the busy test contact by test wiper 50short circuits relay 4;

operates in a buzzer-like manner to advance the wipers 48-51 step bystep in search of an idle directorhen an idle director is reached, whichdirector, it will be assumed, is the one shown in the drawings andreached by way of conductors 5255, switching relay 4, being no longershort circuited, energizes in series with stepping magnet 42. Steppingmagnet 42 does not operate at this time on account of the relativelyhigh resistance of switching relay 4. At armature 46, relay 4disconnects test wiper 50 from the junction of its own winding and thatof magnet 42 and connects it to ground instead, thereby male ing theseized director busy; at armature 47 it closes a point in the operatingcircuit; and at armatures 44 and 45 the said relay 4 connects up thewipers 48 and 49, thereby 5 connecting conductors 19 and 21 of the first20 selector FS to a closed bridge in the seized director including theoutgoing control conductors 52 and 53 and contacts 314 of the senderswitch SS, Fig. 4, in multiple with armature 307 and resting contact.Accordingly, line relay 22 of the first selector FS operates and closesa circuit for the associated release relay 23 .which energizes toprepare the selector for operation.

In the director, release relay 301 energizes over conductor 54responsive to the grounding of conductor 54 through test wiper by relay4 of the director selector DS. At

armature 304, relay 301 removes ground from the restoring conductor 215of the sequence switch S; at armature 306, th1s relay removes groundfrom the restoring conductor 319 over which the release magnets ofcertain of the mechanlsms are operated; and

at armature 305 it connects conductor 112 to the two-step code-controlrelay 401. In this case, it will be assumed that there is no groundpotential on conductor 112 and that relay 401, accordingly, is notoperated at this time.

The circuits are now in readiness for the calling subscriber to dial thedigits of the desired number.

\Vhen the calling subscriber turns his call- 111g device in accordancewith the first office digit, line relay 8 of the trunk circuit TC isdeenergized a corresponding number of times and, upon eachd-eenergization, disconnects the operating conductor from switchingrelay 10 and connects it to ground instead, thereby closing a circuitthrough the working contact and armature 47 wiper 51, conductor 55,series relay 201, Fig. 3, distributing wiper 210 of the sequence switchS, and conductor 221, for vertical magnet 417 of the oflice register OR,Fig. 5. Vertical magnet 417 responds to these impulses of current andraises the wipers 412415, step by step until they come to rest oppositethe desired level of bank contacts. Relay 201 is energized in serieswith vertical magnet 417 upon the first impulse of current and, beingslow acting, maintains its armature attracted throughout the series ofimpulses. At armature 203, relay 201 closes a circuit for the slowacting relay 202, which energizes and prepares at armature 204 a circuitfor stepping magnet 205 of the sequence switch S.

At the end of the series of impulses, relay 201 falls back and completesthe circuit of magnet 205 at armature 203, whereupon magnet 205 advanceswipers 208 and 210 one step and wiper 210 shifts the operating circuitfrom the vertical magnet to the rotary magnet. A moment later, relay 202falls back and opens the circuit of magnet 205 at armature 204.

WVhen the calling subscriber dials the next aigit, the resultingimpulses of current are transmitted to the director over the operatingconductors to wiper 210 of the sequence switch S and thence by way ofconductor 222 to the rotary magnet 416 of the ofiice register OR. Therotary magnet 416 responds to these impulses of current and advances thewipers 412-415 step by step until they come to rest upon the desired setof contacts, which set, it will be assumed, is the one shown in thedrawings and connected to the right hand side of the intermediatedistributing frame IDF by the group of conductors 409.

The sequence switch S is operated one step upon the termination of thesecond digit in the same manner as before and wiper 210 shifts theoperating conductor over to con ductor 231 leading to the operatingmagnet 501 of the digit register DR1.

Since both oflice digits have now been registered, the sender may bestarted now to transmit the digits in the ofiice code. Accordingly,wiper 208 of the sequence switch S grounds the start conductor 216leading to the sender and likewise wi aer 214 of the sending controlsequence switch S thereby starting the sending operation in a manner tobe pointed out below.

Responsive to the dialling of the next digit, the digit register DR 1 isoperated and the wiper 502 is set upon the impulse stop conductorcorresponding to the digit.

Similarly, the digit register DR2 responds to the next digit; the digitregister DR3 responds to the following digit; and the digit register DR4responds to the last digit.

It will be understood, of course, that the sequence switch S operatesone step at the end of each of the digits, as before pointed out, inorder to connect the operating circuit to the stepping proper magnet ineach case to bring about the operation above described. WViper 210 movesoff the contact associated with conductor 234 of the digit register DR4and lands on a dead contact upon the termination of the last digit.WVipers 208 and 210 remain in this position until the director isreleased.

Responsive to the grounding of start conductor 216 by the sequenceswitch S at the end of the transmission of the second office digit, asabove pointed out, ground is intermittently supplied through theinterrupter 320 and the resting contact and armature 311 to the steppingmagnet 315 of the sending switch S5. Accordingly, the stepping magnet315 starts to energize and deenergize under the control of theinterrupter 320. The first energization of stepping magnet 315 resultsin the movement of the associated pawl into engagement h the next notchin the wiper dri*-' ratchet wieel. The wipers themselves are notadvanced at this time, but are ac ced one step upon the subsequentdcenergizmion of magnet 315. When thus occurs, pick-up wiper 316encounters a ground potential on the first bank contact, thereby closinga circuit for the pick-up relay 302. Relay 302 row energizes and atarmature 307 removes the slumt from around the sending contacts 314 orJping magnet 315. At armature 309 relay places ground on armature 312 ofstop relay 303, thereby preparing a locking circuit for the stop relayand closing a circuit over conductor 217 for stepping magnet 211 or" thesequence switch 8, which magnet accordingly energizes and moves theassociated pawl into engagement with the next notch in the wiper drivingratchet wheel preparatory to advancing the Wipers 213and 214 upon thesubsequent energization. As another result of its energization, pick-uprelay 302 grounds conductor 54 at armature 308 so as to maintain thedirector busy and to prevent the premature release of its componentswitching mechanisms in case the calling subscriber should hang upduring the transmission of digit.

The shunt having been removed from around the sending contacts 314 or"stepping magnet 315 of the switch SS at armature 307 of pick-up relay302, the next energirzation of stepping magnet 315 results in an openingat the sending contact 314 of the outgoing control circuit includingconductors and 53. Upon the following dee: ergization of the magnet 315,the wipers 316 and 317 advance one step and the outgoin control circuitis again closed contac s 314. At this time, the stop wiper 317encounters the first impulse stop conductor so that case the digit 1 isthe one being tran itted, the stop relay 303 will energize over thefirst stop conductor. The digit to be transmitted in this case, however,is not the digit 1 butis the digit 9 instead. Accordingly, the sendingoperation is not stopped at this point but t continues in terrupteduntil nine interr K ve Leon produced in the outgoing centre circuit atthe sending contacts 314. During the ninth opening in the outgoingcontrol circuit, the stop wiper 317 is standing on the eighth impulsestop conductor. Accordingly, when stepping magnet 315 of the sendingswitch SS again falls back, it closes the outgoing control circuit atcontacts 314 and at the same time advances wipers 316 and 317 anotherstep and wiper 317 encounters the ninth impulse stop conductor.Thereupon a circuit is completed for step relay 303 as follows: Fromground by way of the start conductor 216, stop conductor control wiper214 of the sequence switch S, the first codedigit stop conductor 241,Wiper 412 of the office register OR, the bank contact upon which it isstanding,- the upper conductor in the group labeled 409, the associatedterminal on the IDF, the IDF jumper connecting this terminal with theterminal in which conductor 404 terminates, conductor 404, armature 402and its resting contact, armature 403 and its resting contact, andconductor 405 to the ninth impulse stop conductor.v From the ninthimpulse stop conductor, the circuit continues to the associated contactin the lower bank of the sending switch SS and from thence by way of thestop wiper 317 to battery through stop relay 303. Stop relay 303energizes over this circuit and at armature 310 places a shunt aroundthe sending contacts 314, thereby terminating the transmission of thedigit. At armature 312,- relay 303 removes ground from conductor 217 andcloses a locking circuit for itself.

Responsive to the removal of ground from conductor 217, stepping magnet211 of the sequence switch S deenergizes and advances the wipers 213 and214 one step. Wiper 214 disconnects ground from the first code digitstop conductor 241 and places ground on the second stop conductor 222.

As another result of its energization, stop relay 303 disconnectsstepping magnet 315 of the sending switch SS from the interrupter 320and connects it instead through the local interrupter contacts 313 toWiper 316. Magnet 315 is self-interrupting in this circuit. Accordingly,magnet 315 operates in a buzzer-like manner to advance the wipers 316and 317 to their normal position 'When the normal position is reached,wiper 316 encounters an ungrounded contact, whereupon the operation ofmagnet 315 ceases and the circuit of pick-up relay 302 is opened. Relay302, however, being slow acting, does not d-eenergize for the timebeing.

In the first selector FS, Fig. 1, line relay 22 falls back once for eachinterruption pro duced in its circuit by the director as above pointedout, with the result that the selector is operated in the usual mannerto bring its wipers 25-27 opposite the ninth level of bank contacts.

At the end of the vertical movement of the first selector PS, the usualautomatic trunk hunting operation is initiated in the usual manner withthe result that wipers 27 are brought into engagement with an idletrunk, which trunk, it will be assumed, is the one comprising conductors2830 and extending to the repeater B, Fig. 2. That being the case,conductors 19 and 21 are extended through to the wipers 25 and 27 and toconductors 28 and 30 upon the operation of switching relay 24 when theidle trunk is reached. Also, test wiper 26 is disconnected from the testcircuit and is connected in stead to the grounded release trunkconductor 20, thereby making the seized trunk busy immediately.

Responsive to the connecting up of the line wipers of the first selectorFS, line relay 101 of the repeater B, Fig. 2, energizes through the lefthand repeating coil windings and over conductors 23 and 30 and closes atarmature 103 a circuit for release relay 102. When this occurs, relay102 pulls up and places ground on release trunk conductor 29 at armature105 so as to maintain the connection established after the release relay23 of the first selector FS has fallen back as it shortly does and afterrelease relay 9 of the trunk circuit TC has fallen back, which will takeplace upon the switchthrough operation of the director, as will bepointed out subsequently.

In the repeater R, as a further result of the energization of releaserelay 102, it closes at armature 106 a point in the circuit of chainrelay 111 in the chain relay group CRG. This, however, does not resultin the energization of relay 111 unless all the other repeatersaccessible to the first selector FS from the ninth level are busy.

As a still further result of the energization of the line relay 101 ofthe repeater B, it closes at armature 104 a bridge cross conductors 107and 108 through the right hand repeating coil winding. When this occurs,the selector switch in which conductors 107 and 108 terminate in thedistant otlice is prepared for operation in the usual manner.

In the director, relay 302 falls back after the interval for which it isadjusted, and at armature 309 opens the locking circuit of relay 303.Relay 303, however, being slow acting, does not fall back for aninterval.

It may be pointed out that the interval of time required for relays 302and 303 to fall back one after the other is suiiicient to permit thetrunk hunting operation of the selectors to take place. I,

When relay 303 falls back, it disconnects stepping magnet 315 from theself-interrupting circuit and connects it instead to the interrupter320, whereupon stepping magnet 315 again starts to operate under thecontrol of the interrupter 320 and the second digit in the number istransmitted in a manner similar to the first digit. 7

By referring to the intermediate distributingframe IDF, Fig. 5, it maybe seen that the second bank contact in the group upon which the wipersof the office register OR are now standing is cross connected to thefifth impulse stop conductor. Accordingly, stop relay 303 energizes andterminates the second digit when five impulses have been transmitted.The circuit over which conductor 303 operates is as follows: From groundby way of the stop-conductorcontrol wiper 214 of the sequence switch S,the second code digit stop conductor 242, wiper 413, the bank contactupon which it is standing, the associated jumper on the intermediatedistributing frame IDF, the fifth impulse stop conductor, the associatedcontact in the sending-switch bank, stop Wiper 317, and stop relay 303to battery. The energization of stop relay 302 results in thetermination of the second digit in the same manner as the first, and thesequence switch S advances one step, thereby disconnecting ground fromthe code-digit stop conductor 242 and connecting it instead to the thirdcode digit stop conductor 243.

Responsive to the transmission of the second code digit, the incomingselector in use in the distant oflice raises its wipers opposite thefifth level of bank contacts and selects an idle office selector, eitherin the same oflice or in still another office, depend ing of course uponthe trunking arrange- .ment.

After the usual interval, relays 302 and 303 both fall back and thethird code digit is transmitted in the same manner as the two precedingdigits.

Upon referring to the intermediate .distributing frame IDF, it may benoted that the third bank contact of the set in use is cross connectedon the intermediate distributing frame to the fourth impulse stop.conductor. Accordingly, the third code digit is the digit 4, and thestop relay 303 of the sender is energized through the third codedigitstop conductor 243, wiper 414, the jumper on the intermediatedistributing frame and the fourth impulse stop conductor to terminatethe digit as soon as four interruptions have been produced in theoutgoing control circuit.

The advance of the sequence switch S takes place in the usual mannerupon the energization of stop relay 303. Accordingly, wiper 214 removesground from the third code digit stop conductor 243 and placesgroundupon the fourth code-digit stop conductor 244. In this case, thereare only three digits in the code of the called oflice. Therefore,thefourth code-digit stop conduc tor is not used to terminate a digit, butit is,

nevertheless, necessary to advance the sequence switch S through itsfourth codedigit position. Accordingly, the bank contact engaged bywiper 415 is cross connected on the intermediate distributing frame IDFto the skip conductor 218. That being the case, when the fourth wiper415 is grounded over conductor 244, ground is extended across theintermediate distributing frame to the skip conductor 218 and thencethrough the self-interrupting contacts 212 to the stepping magnet 211 ofthe sequence switch S. Stepping magnet 211 energizes and interrupts itsown circuit, whereupon it deenergizes and advances the wipers 213 and214 one step. VZiper 214 accordingly removes ground from conductor 244and extends it to the first subscriber-digit stop conductor 251.

Responsive to the transmission of the third code digit, the ofliceselector seized at the end of the second code digit raises its wipersopposite the fourth level and selects a trunk line extending to athousands selector in the desired oflice.

In the director, the sender now transmits the four subscriber digits,one after the other, with the usual interval between the digitsintroduced by the slow action of the relays 302 and 303, the foursubscriber-digit stopconductors 251-254 being grounded one after theother in order by the sequence switch S under the control of the sendingswitch.

At the end of the transmission of the fourth subscriber digit, wiper 214advances from its eighth position to its ninth position, therebyremoving ground from the fourth subscriber digit stop conductor 254 andplacing ground upon the switching branch of the operating conductor 55.When this occurs, a circuit is closed over conductor 55 through thecontact and wiper 51 of the director selector DS, armature 47 and itsworking contact, and armature 12 and its working contact for switchingrelay 10 of the trunk circuit TC. Switching relay 10 energizes over thiscircuit and locks itself to the grounded release trunk conductor atarmature 17 and at armatures 16 and 18 disconnects conductors 5 and 7from line relay 8 and extends them to conductors 19 and 21, at the sametime disconnecting conductors 19 and 21 from the outgoing controlcircuit of the director, thereby leaving the established connectionunder the direct control of the calling line.

Line relay 8 now falls back and opens the circuit of release relay 9 atarmature 11. Accordingly, release relay 9 deenergizes after the intervalfor which it is adjusted and removes ground from the release trunkconductor at armature 13, leaving the established 'connectlon held byground supplied to the release trunk conductor at the repeater R,

Fig. 2. At armature 15, relay 9 opens a further point in the connectionpreviously existing between test wiper 50 and the junction of relay 4and stepping magnet 42 of the director selector DS, and at armature 14disconnects ground from switching relay 4, whereupon relay 4 falls backand frees the director.

In the director, relay 301 falls back responsive to the removal ofground from the release trunk conductor 54 when the director is freed.At armature 304, relay 301 places ground on the restoring conductor 215thereby closing a circuit through wiper 213 and contacts 212 for thestepping magnet 211 of the sequence switch S. When this occurs, theself-interrupting stepping magnet 211 advances the wiper s 213 and 214through their remaining step to their normal position.

At armature 306, relay 301 grounds the release conductor 319, therebysupplying current for operating the release magnets of the digitregisters DR1DR4; the release magnet of the office register OR; and therelease magnet of the sequence switch S.v Accordingly, the releasemagnets mentioned operate and restore the respective switches to theirnormal position. For example, release magnet 418 of the office registerOR operates through off normal contacts 419, and release magnet 206 ofthe sequence switch S operates through oif normal contacts 207. Thecircuits of the various release magnets are opened in the usual mannerat the respective associated off normal contacts.

At armature 305, relay 301 disconnects conductor 112 from conductor 318.

Regarding relays 302 and 303, it may be pointed out that relay 302obviously falls back prior to the deenergization of relay 301 andremoves ground from conductor 54 at armature 308 to permit relay 301 tofall back. Relay 303 falls back because its locking circuit is opened atarmature 309 of relay 302.

The desired connection has now been completed in the called officethrough the medium of a thousands selector, a hundreds selector, and aconnector, and the called subscribers bell is rung in the usual mannerprovided the line is idle, in which case the conversation takes place inthe usual manner when the called subscriber responds.

When the calling subscriber replaces his receiver at the end of theconversation, line relay 101 of the repeater B, Fig. 2, falls back andopens the bridge across conductors 107 and 108 at armature 104, with theresult that the connection extending to the distant otfice is releasedin the usual manner. At armature 103, line relay 101 opens the circuitof release relay 102 which deenergizes after the usual interval andopens at armature 106 a point in the circuit of chain relay 111. At

armature 105, relay 102 removes ground from release trunk conductor 29,whereupon the first selector FS releases in the usual manner andswitching relay 10 of the trunk circuit TC falls back. The entireconnection is now released. Assuming now that all trunks accessible tothe first selector FS on the ninth level are busy, the release relays ofall the repeaters of such trunks, including the release relay 102 of therepeater R, are energized and a chain circuit is completed for the ninthlevel chain relay 111 of the chain relay group CRG. hen this occurs,relay 111 energizes and connects ground through the resistance 122 toconductor 112 at armature 123. In case the director shown in Figs. 36,is seized at this time, the two-step relay 401, Fig. 5, energizes overconductor 112, through the working contact and armature 305, and overconductor 318. This relay operates through its first step only at thistime, due to the fact that it is energized through resistance 122, Fig.2. Accordingly, the first step armature 403 is operated, but the secondstep armature 402 is not operated. Armature 403 disconnects conductor404 from the ninth impulse stop conductor and connects it to the sixthimpulse stop conductor by way of the conductor 406. Accordingly, thefirst digit to be transmitted (in case the call is an outgoing one) isthe digitti instead of the digit 9 and in case the first selector FS isthe one in use, this selector raises its wipers opposite the sixth level(instead of opposite the ninth level) and selects an idle trunk line inthe group to which the repeater R belongs.

Assuming now that all the sixth level trunks become busy, all therelease relays of the various repeaters associated with these trunks,including release relay 102 of the repeater R, are energized.Accordingly, a chain circuit is closed for chain relay 110 of the chainrelay group (JR-G. That being the case, relay 110 pulls up and shortcircuits the resistance 122 at armature 120 and, in case the ninth levelchain relay 111 is energized, direct ground is placed on conductor 112,with the result that the two-step relay 401, Fig. 5, is operated in casethe director shown in the drawings is taken for use at this time. Relay401 operates through both its first step and its second step at thistime and at armature 402 connects conductor 404 to the third impulsestop conductor by way of conductor 407, thereby pie-determining that thefirst digit to be transmitted in case an outgoing call is made at thistime is the digit 3.

It will be understood, of course, that the chain relays are providedwith sur'licient contacts to enable a conductor similar to 112 to beprovided for each of the directors in the group which normally transmitsthe digit 9 to send the outgoing calls out over the ninth level of thefirst selectors.

Regarding the directors in the group which normally transmits the digit6, it may be pointed out that conductor 113, Fig. 2, extends to one ofthe directors in this group and corresponds to conductor 112 in its manner of connection in the director to which it extends. It will be notedthat when the sixth level chain relay 110 pulls up, ground is placed onconductor 113 at armature 119, through the resistance 118, so as to pullthe two-step code-changing relay in the associated director half way incase the director is in use, thereby shifting the stop circuit so thatthe first outgoing digit to be transmitted is the digit 3 instead of thedigit 6.

It will be noted that when the third level chain relay 109 is operatedsimultaneously with the energization of relay 110, direct gro nd througharmatures 117 and 119 is placed on conductor 115, so as to pull the codechanging relay in the associated director all the way up to shift thestop circuit so that the first outgoing digit to be transmitter is thedigit 9.

The conductor 114 is typical of the control conductors of the thirdgroup of director i. e., the group which normally transmits calls to thethird level of the first selectors. When the third level chain relay109' pulls up, ground through resistance 115 placed on conductor 114 atarmature 116 so 'asto operate the code changing relay of the associateddirector half way in case the director is in use and this shifts thestop circuit so that the first outgoing digit to be transmitted is thedigit 9 instead of the digit 3.

It will be noted that in case the third and ninth level chain relays 109and .111 are operated simultaneously, ground through armatures 121 and116 in series is placed on conductor 114 to pull up the associated chainrelay all the way to shift the stop circuit so that the digit 6 is thefirst outgoing digit to be transmitted in case the associated directoris in use at this time.

t will be appreciated, of course, that the conductors 113 and 114, likethe conductor 112, are each individual to one director and thatsufficient conductors connected similarly must be provided to take careof the remaining directors in these two groups.

In order to explain still another function of the director shown in thedrawings, it will he assumed that the trunk extending through the trunkcircuit TO to the first selector FS is seized at the bank contacts 24,and that when the director selector DS operates it seizes the directorshown in the drawings, which is accordingly prepared for operation inthe usual manner. It will he assumed further that the number assigned tothe local oi'iice is 30 and that the 50 fices but each office has itsown code.

calling subscriber is calling a local line. Accordingly, the callingsubscriber dials the two oflice digits 3 and 0 assigned to the localoiiice. The oflice register OR raises its wipers 4124L15 opposite thethird level of bank contacts responsive to the first ofiice digit 3.

Responsive to the second ofiice digit 0, the ethos register OR rotatesits wipers step by step until they land upon the tenth set of bankcontacts (not shown) in the third level. hen this occurs, the tenthrotary step contacts, Fig. 5, (which operate on the third 'level only)connect ground to the switching branch of the operating conductor 55,thereby closing the usual switching circuit for switching relay 10 ofthe trunk circuit TC. That being the case, switching relay 10 operateswith the result that'the call is switched through to the unoperatedfirst selector FS and the director shown in the drawings is freed in theusual manner.

When the subscriber dials the thousands digit, either 4 or 5, the firstselector F S operates as a thousands selector to select an idle hundredsselector in the elected thousands group.

lVhen the calling subscriber dials the three remaining digits in thedesired numher, the seized hundreds selector and a connector switch areoperated to extend the connection to the desired local line.

The foregoing arrangement is particularly desirable in a situation likethe one assumed in the present case, because, in this case, the ratio.of local calls to outgoing calls is very large and, since no director isneeded to route the local calls, (the director being freed immediatelyupon the termination of the dialling of the office digits on localcalls), the number of directors required is very greatly reduced.

Reference will now be had again to Fig. 5 in order to explain that thearmatures 402 and 408 of the two-step code-changing relay 401 may beused to change the same digits in as many codes as desired. For example,the same group of outgoingtrunk lines is used for calls to all thedistant of- However, these codes all have the same first digit and, asmay be expected, the first code digit stop conductor is cross connectedon the intermediate distributing frame IDF to the common terminal inwhich conductor 404 terminates. For example, the contact associated withthe first of the conductors in the group 4.09 is cross connected to theabove mentioned common contact, as hereinbefore explained, and the twoother groups shown,

namely, 408 and 410 have their first conductors cross connected to theabove-named chinmon contact. Although no other contact groupsrepresenting individual positions of the office register OR are shown,it will be assumed that the remaining bank contact sets are crossconnected on the IDF in the same way as regards the first code digitposition, and it will be understood that the other contacts of such setsare cross connected in accordance with the remaining digits in therespective ofiice codes.

What is claimed is:

1. In a telephone system, an automatic switch, a plurality of groups oflines accessible to said switch, a sending apparatus for transmittingimpulses to bring said switch into operative relation with one of .saidgroups of lines, and means responsive to the condition of all lines insaid group being busy for altering said sending apparatus before itstarts so that it will send a difierent series'of impulses to bring saidswitch into operative relation with another one of said plurality ofgroups of lines.

2. In a telephone system, a director including a register switch and asender, an automatic switch, means operated during the course of a callfor extending a connection to said automatic switch and for temporarilyassociating said director with said automatic switch, means foroperating said register switch over the calling line, said sender beingsubsequently controlled by said register switch to transmit a digit tosaid switch in accordance with the position assumed by said registerswitch, and means controlled in accordance with the condition of thetrunk lines accessible to said switch for modifying the register controlto cause said sender to transmit a different digit to said switch.

3. In a telephone system, a first oilice, a second oflice, two groups oftrunk lines extending from said first oflice to said second oflice, adirector in said first office normally set to translate the ofiicedesignation of said second oflice into a code which will trunk a callover a trunk line in the first of said groups, and means effective incase all the trunks of said first group are busy for changing said codebefore transmission so that the call will be trunked over a trunk linein the second of said groups. I

4. In a telephone system, a first oilice, a second ofiice, three groupsof trunk lines extending from said first office to said second oflice, adirector in said first oflice normally set to translate the oflicedesignation of said second oflice into a code which will trunk a callover a trunk line in the first of said groups, means responsive to abusy condi tion of said first group for changing the code beforetransmission to cause the call to be trunked over a trunk line in thesecond group, and means responsive in case both the first and secondgroups are busy for changing the code a different way so as to trunk thecall over a trunk line in the third group.

5. In a telephone system, a first ofiice, a :J

matic switching apparatus, and means responsive to a heavytrafiic-condition within a trunk group "for altering, the registersender that the sending. apparatus is c ontrolledover the saidconnection to said conductor to send out a different digit to theautomatic switching apparatus.

17. In an automatic telephone exchange system, two regist er'senders, agroup ,of automatic switches arranged to be controlled by said register"senders, said automatic switches having multipled bank contactsarranged in groups corresponding to different digit values, digitconnections in the first register sender effective when a givendesignation 1s set uptherein for causing one of said automatic switchesto be driven into association with a group of bank contactscorresponding'to a first digit'-val ue,digit connections'in-thesecondregister sender effective when the same designation is set uptherein for causing one of said automatic swltches to be drlven intoassociatlon wltha contact group corresponding'to a second digit-value,and trunk lines extendingfrom' thereto, register senders equal-in numberto;

said plurality of levels and corresponding thereto, respectively, meansfor associating any one of said register senders with any one of saidswitches, and means effective when the said common designation is set upin any one of said register senders for operating the associated. one ofsaid automatic switches into association with the level thereof whichcorresponds to the register sender:

in use, so that the level ofcontacts .with

which connection is made in response to the" said designation isdependent upon the register sender on which said designation is set up.a v.

19. In a telephone exchange system, a group of selector switches havingmultipled bank contacts divided into groups corresponding to difi'erentdigit values, said selector switches being arranged to extendconnections responsive to designations transmitted to the exchange fromcalling lines,

means including register senders; interposed between said call ng linesand sald selector of groups. of trunks accessible to said sel'ectors-and-e'xtending to the second" ex-" change -a groupofdirectorsinthe first exchange, means responsive to the removalof the receiver on aline in said 'first' exchange for selectingan'idle selector and forconnect} ingup an idle director, means forregistew ing' the designationof -the second exchange in any connected director, means in suchdirector fortransmitting a digit to operate the first selector' intoassociation with one of said groups .of'trunk lines, and a plurality ofdifferent translating circuits in said di.- rectors whereby the digitstransmitted to said first selector on =successivefcallsare varieddepending on the'directo-nused in' each call in 'or'der to "distribute'the" traffic to said plurality ofgrcups oftrunk'lines; 21. Inatelephone exchange,1agroup of selectors, 'a' grouip ofdirecto r's,subscribers lines, means responsive to a calling signal" on asubscribers linejfor, temporarily asso ciating a directorwith 'such'line, means for registering an exchange designation in said director,means in said director responsive thereto for sending-a digit to one ofsaid selectors, means responsive to the same identical calling signal onanother of sai'dsubscriberslines for associating another one of saiddirectors therewith, and means in the second director responsive to theregistration of the ,same "exchange designation for send-"- ing adifl'erent digitto said selector. The method o f securing a large group,of trunks without secondary line switches," in a systemnsing selectors'havingfbank contacts divided i'nto groups which are smaller than thetrunk group desired, which con-- sists assigning "the 'trunksjof thelarge group to anumber' of selector b ankgroups, in providing directorsto "operate the select ors to'select said bank groups, in routingcalling lines 'to' said directors'in random fashion soithatj'any callingline may use any director, and in translating the" designation of thesaid large trunk group differ ently in thedifierent directors, therebeing asmany different translations used as there are selector'bankgroups assigned to said trunks. V v 1 In witness whereof, Ihereunto subscribe;

LEONARD L. RUGGL sL switches for transmitting different digit values tosaid selectors responsive to 1 the same designation, whereby theselectors are variously positioned on a plurality of contact groups, andseparate trunk lines extending from each of the last-named contactgroups to the same numerical group of the 5 exchange. a

